FARM DRAINAGE 



239 



The main drains should be located in the lowest 

 parts of the fields, indicated by courses taken by 

 water after a rain or by small streams running 

 through the farm. 



The lateral drains, if surface or open ditch drains, 

 should run across the slopes; if under drains, they 

 should run up and down the slopes. 



Grade or slope of the drain. 



The grade of the drain should be sufficient to 

 cause a flow of the water. In the case of open 

 ditches it should not be steep enough to cause too 

 rapid a current and a consequent serious washing 

 of the banks of the ditch. Large, deep ditches will 

 carry water with a grade of one inch to a hundred 

 feet. 



Tile drains. 



Covered or under drains are made of brush, poles, 

 planks, stones, tiles, etc. (Figs. 83-84). Where tiles 

 can be obtained at reasonable prices they are con- 

 sidered best. Tiles are made of clay and are burnt 

 like brick. They are more lasting than wood and 

 are easier and cheaper to lay than stone, unless the 

 stone must be gotten rid of. 



The most approved form of drain tile is the round 

 or circular form. These are made in sizes ranging 

 from two and one-half to six and eight inches in 

 diameter, and in pieces one foot in length. 



The size used depends on the length of the drain, 

 the amount of water to carry, the frequency of 

 heavy rainfalls and the character of the soil. 



The distance apart varies from twenty-five feet in 



